1. Field of the Invention
This invention relates generally to diaphragms having springless rims, and more particularly to springless rimmed diaphragms which provide dome shaped portions affixed to the rims and especially adapted for use in birth control.
2. Description of the Prior Art
Conventionally used diaphragms are provided with a dome shaped body portion and a rim which is reinforced with a coiled spring imbeded therein. Diaphragms have been in wide-spread use as birth control devices for over fifty years, and during this time the industry has not made any appreciable change in the form, shape or method of manufacturing of these diaphragms. The commercial diaphragms are all round in shape and contain such coiled springs in the rims thereof, and are typically made of natural rubber.
In the conventional manufacturing method, a spring coil of the desired size is encapsulated in gum rubber, but the resulting combination is not vulcanized until the dome is formed and joined to the rim. This is accomplished by placing the encapsulated rim into a suitably sized mold which is provided with a dome shaped portion. An additional quantity of the gum rubber is then added to the mold which is then closed under heat and pressure to force this additional quantity of rubber downwardly over the dome portion of the mold and to bond the thus-molded dome to the spring-rim combination, by vulcanization.
In the construction of the above type of diaphragms, extreme problems have existed over the years in successfully producing spring rimmed devices with any reasonable degree of reliability and efficiency, and there has resulted a need to discard a high percentage of the products so produced due to flaws in the molded products, particularly in the spring rimmed portions thereof. As a result of this procedure and the attendant extremely high rate of discards, devices of the conventional type have been merchandised at a high price.
From experiences with molding devices in which such spring rimmed portions are provided, it has been substantially impossible to locate the spring, constituting an integral part of the rim, centrally within the finally vulcanized rim. In many instances, part of the spring would be exposed at the periphery of the rim, or would be so close to exposure as to render the molded product a reject upon inspection thereof. The failure to locate the spring centrally in the molded rim necessitates rejection of the molded product since corrosion of the spring is a possible consequence of incomplete encapsulation with the gum rubber after vulcanization. Also, the wearer of the device can experience some discomfort due to irritation which can result to sensitive body surfaces which come into contact with any exposed spring sections. Of course, the exposed springs could also serve as the focal point for collection of bacteria which would make sterilization of the devices more difficult, and even if such disadvantages could be successfully overcome, the exposed springs would not be aesthetically acceptable to the user.
Illustrative of the various diaphragms which have been heretofore proposed are those disclosed in U.S. Pat. No. 2,087,610 which relates to devices composed of flexible resilient material such as rubber and provided with an oval shaped rim comprising a coiled spring imbeded in a bead-like rim composed of the diaphragm material. The rim is provided with an off-center pocket or dome adapted to be filled with an antiseptic jelly before the diaphragm is inserted into the wearer.
U.S. Pat. No. 2,529,363 relates to a diaphragm having a complex arrangement of an expansible helical spring and wires in the rim of the device which is in turn composed of soft rubber or latex.
U.S. Pat. No. 2,540,932 illustrates the complexity in the manufacturing methods employed by the prior art. An oval helical spring is assembled with two opposing flat springs positioned therewithin. Since machining of oval shaped molds is expensive, the patentee employs a circular shaped mold and forces the oval spring assembly onto the circular mold. The molding operation by closing the mold and forming the dome portion and vulcanizing the device, followed by removal of the device from the mold, whereupon the rim then is allowed to resume its oval shape. Such distortion of the oval spring during the molding operation can result in an increased tendency of the spring to come to the surface of the rim bead, thereby leading to rejected molded products.
In U.S. Pat. No. 2,294,589, the patentee employs an oval shaped die onto which the spring assembly is placed prior to encapsulation of the spring and formation of the dome portion of the diaphragm. Again, this method does not avoid the problems associated with the high turbulence during application of heat and pressure in the molding step which causes the above-noted exposure of springs in the finally molded diaphragm.
The devices of U.S. Pat. No. 3,169,894 emloys two opposing pins within the coiled spring, and U.S. Pat. No. 3,169,522 molds an additional portion of the diaphragm material on the dome at the lower periphery thereof to allow the molded product to be withdrawn from the mold and the rim-spring portion to be rolled up one complete turn to ensure that the spring is fully covered by the rubber. The resulting device in U.S. Pat. No. 3,169,522 is then treated to bond the turned up rim onto the dome.
The more recent attempts at improvements in the conventional devices have not curred the above discussed difficulties of high rejection rates and also variously introduce additional complex steps in the manufacturing process.
In U.S. Pat. No. 4,261,352, the rim of the diaphragm houses an inner reinforcing ring, held loosely therewithin, one end of which is sized so as to telescope into the opposite end, to permit size adjustment.
U.S. Pat. No. 4,300,544 employs a rim which is discontinuous and which varies in thickness about the circumference thereof at the side in the rim which is opposite the anterior rim opening. In another embodiment, the rim is formed so as to provide overlapping ends. In these devices, the rim is bonded to a flat sheet member on which is provided a sponge which acts as the contraceptive when placed in the user.